linux-kernel - Re: [PATCH] coccinelle: assign signed result to unsigned variable

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Date:	Sat, 26 Sep 2015 09:45:15 +0200
From:	SF Markus Elfring <elfring@...rs.sourceforge.net>
To:	Andrzej Hajda <a.hajda@...sung.com>
Cc:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Gilles Muller <Gilles.Muller@...6.fr>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Michal Marek <mmarek@...e.com>,
	Nicolas Palix <nicolas.palix@...g.fr>,
	kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
	cocci@...teme.lip6.fr
Subject: Re: [PATCH] coccinelle: assign signed result to unsigned variable

> Generally I want to catch all assignments of signed function result to unsigned var.

Such a static source code analysis will be useful to some degree.

> In this script I have implemented it this way:
> 1. Look for all assignments 'unsigned = signed' (rs rule).
> 2. Check if signed from rs rule looks as a function call.

I recommend to reconsider a few implementation details because I have got
the impression that this check sequence is inappropriate.

> Is there better way to do it?

I suggest to fix expression weaknesses and a design mistake in this SmPL approach.

I guess that you want to determine functions with a signed return type first
before corresponding variable assignments will be checked further.
* Would you like to collect function names for this purpose by a general analysis
  of more source files?
  (How do you think about to store them in a dedicated database?)

* Which couple of function calls will be interesting for you?

* Should the search approach take also recursively included files into account?

Regards,
Markus
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